The musician, 30, shared the news with her horrified fans this week - and even posted pictures of the cheeky insect!
The 'Closest Thing To Crazy' star said she only discovered her intruder after hearing noises in her ear - shudder!
She tweeted: "So I had a rustling in my ear for a week and went to the doctor to have it checked out this morning. THIS little fella is what they found!"
As her thousands of fans reacted to the gross news, Katie shared more information and pictures.
She wrote: "Basically I used these old in-ear monitors to block out sound on a flight, little spider must have been in them and crawled inside my ear and stayed there for the week. It was no hassle at all, apart from the occasional shuffling noises..."
Katie - who coincidentally had a 2006 single called 'Spider's Web' - also assured fans that the offending mite was alive and well after the experience!
She wrote: "Though the thing looked TERRIFYING up-close on the doctor's camera, once he took him out (using a micro Hoover) it was pretty small, and now it's in this little test tube, alive and seemingly fine."
We are NEVER using headphones again!
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Watch Katie Melua's official video to her 2003 single 'Closest Thing To Crazy':